Here’s the fix-first order that actually makes things better:

1) Freeze the surface, fix the contract

• Contract-first APIs: publish one source of truth per interface.
  • REST → OpenAPI 3.1
  • Events/queues → AsyncAPI (+ JSON Schema for payloads)
  • GraphQL → schema.graphql with versioned @deprecated
• One error envelope everywhere (no raw strings, no 200-with-error):

{
  "error": {
    "code": "RESOURCE_NOT_FOUND",
    "message": "User 42 not found",
    "traceId": "01H…",
    "details": []
  }
}

• Stable conventions: ISO-8601 times, UTC, snake_or_camel (pick one), idempotency keys for POST, cursor pagination, rate limiting headers.

2) Put a membrane in front

• API Gateway + BFF (Backend-for-Frontend): one façade per app that:
  • Enforces schema (rejects non-conformant payloads).
  • Normalizes auth, CORS, caching, pagination.
  • Hides backend churn so the front stays simple and “symmetrical.”

3) Make comms observable (so you can prove it works)

• Correlation/tracing: accept/generate W3C traceparent; propagate as X-Request-ID. Add middleware to log it on every hop.
• Structured logs (JSON) with traceId, spanId, latencyMs, status, route.
• Health endpoints: GET /healthz (liveness) and GET /readyz (readiness) with dependency checks.
• SLOs: e.g., “p95 latency ≤ 250 ms, availability ≥ 99.9%” per endpoint, and alerts tied to them.

4) Reduce chatty, brittle calls

• Batch/shape endpoints to match UI needs (or use GraphQL for field-selects).
• Caching rules: strong ETags, Cache-Control, 304 flows; shard hot keys behind the gateway.
• Resilience: timeouts, retries w/ jitter, circuit breakers; DLQs for events.

5) Guard it in CI so it can’t regress

• Contract tests (e.g., Pact) between producers/consumers.
• Schema registry (even a repo folder) with semver and breaking-change checks.
• Head/order linter on the HTML shell if you want behind-the-scenes symmetry (basics → hints → styles → data → scripts).

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Two-week thin-slice that changes everything

1. Pick one customer-facing flow (e.g., “fetch user + orders”).
2. Write its OpenAPI & error model.
3. Stand up a small BFF that enforces the spec and adds correlation IDs.
4. Add /healthz /readyz, structured logs, and SLOs for these routes.
5. Gate deploys with schema diff + contract tests.
6. Point the UI at this BFF. Measure p95 & error rate. Only then add “tools.”

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Tiny skeletons you can drop in today

Correlation ID middleware (pseudo-JS):

export function withTrace(req, res, next) {
  const trace = req.headers['traceparent'] || `00-${crypto.randomUUID().replace(/-/g,'')}–${crypto.randomUUID().slice(0,16)}-01`;
  res.setHeader('traceparent', trace);
  req.traceId = trace;
  next();
}

Readiness JSON:

{
  "status":"ready",
  "checks":{
    "db":{"status":"pass","latencyMs":12},
    "queue":{"status":"pass"},
    "deps":{"userService":"pass","inventory":"warn"}
  }
}

OpenAPI stub (excerpt):

openapi: 3.1.0
info: { title: Orders API, version: 1.2.0 }
paths:
  /users/{id}/orders:
    get:
      parameters:
        - in: path; name: id; required: true; schema: { type: string }
        - in: query; name: cursor; schema: { type: string }
        - in: query; name: limit; schema: { type: integer, maximum: 100, default: 20 }
      responses:
        '200': { $ref: '#/components/responses/OrdersPage' }
        '404': { $ref: '#/components/responses/Error' }
components:
  responses:
    Error:
      description: Error envelope
      content: { application/json: { schema: { $ref: '#/components/schemas/Error' } } }
  schemas:
    Error:
      type: object
      required: [error]
      properties:
        error:
          type: object
          required: [code, message, traceId]
          properties:
            code: { type: string }
            message: { type: string }
            traceId: { type: string }

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Bottom line

You’re right: tools don’t fix incoherent comms. Establish the contract, put a gateway/BFF membrane in front, add tracing + health + SLOs, and enforce all of it in CI. Once the backend speaks clearly and consistently, the UI gets simpler, performance improves, and the “keep adding tools” treadmill stops.